U.S. patent application number 13/364634 was filed with the patent office on 2012-08-02 for bone fixation assembly.
Invention is credited to Stefan Knueppel.
Application Number | 20120197257 13/364634 |
Document ID | / |
Family ID | 45689012 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120197257 |
Kind Code |
A1 |
Knueppel; Stefan |
August 2, 2012 |
Bone Fixation Assembly
Abstract
A bone fixation system includes at least one bone fixation
member and a bone fixation instrument. The bone fixation member
includes a strap and a locking mechanism. The strap can be pulled
through the locking mechanism so as to form a loop about a target
bone so as to secure first and second bone segments in an
approximated, compressed configuration. The bone fixation
instrument is configured to apply tension to the loop about the
target bone. The fixation instrument includes a tension assembly
that is configured to secure a free end of the bone fixation member
to the fixation instrument. The tension assembly is further
configured to pull the free end so as to increase tension in the
loop while the tension in the loop is less than a select tension.
The fixation instrument further includes a cutter assembly.
Inventors: |
Knueppel; Stefan; (Oberdorf,
CH) |
Family ID: |
45689012 |
Appl. No.: |
13/364634 |
Filed: |
February 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13019907 |
Feb 2, 2011 |
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13364634 |
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Current U.S.
Class: |
606/74 |
Current CPC
Class: |
A61B 17/8872 20130101;
A61B 17/8869 20130101; A61B 2017/06052 20130101; A61B 2017/0496
20130101; A61B 17/8863 20130101; A61B 2017/00407 20130101; A61B
17/823 20130101; B65B 13/027 20130101; A61B 2090/032 20160201; A61B
2017/0454 20130101 |
Class at
Publication: |
606/74 |
International
Class: |
A61B 17/82 20060101
A61B017/82 |
Claims
1. A bone fixation instrument configured to apply tension to a bone
fixation member so as to tighten the bone fixation member about a
target bone, the fixation instrument comprising: a body defining a
front end and an opposed rear end; a grip configured to secure a
free end of the fixation member to the fixation instrument; a
traveler that is connected to the grip such that the grip moves
rearward along with the traveler so as to increase tension in the
bone fixation member; an actuator operatively coupled to the
traveler, the actuator configured to move from an initial position
toward a tension position in response to an applied force, thereby
biasing the traveler to move rearward; and a tension limiter
connected between the actuator and the traveler, wherein the
tension limiter allows the traveler to move rearward when the
tension in the bone fixation member is less than a select tension,
and prevents the traveler from moving rearward when the tension in
the bone fixation member reaches the select tension.
2. The bone fixation instrument as recited in claim 1, wherein the
grip is movable between a disengaged position and an engaged
position, such that when the grip is in the disengaged position,
the grip defines a gap sized to receive the bone fixation member,
and when the grip is in the engaged position, the gap is reduced
such that the grip secures the bone fixation member to the bone
fixation instrument.
3. The bone fixation instrument as recited in claim 1, wherein the
grip further comprises first and second grip members, such that one
of the grip members is movable between a disengaged position and an
engaged position, such that the movable grip member is spaced apart
further from the other grip member in the disengaged position than
in the engaged position.
4. The bone fixation instrument as recited in claim 3, wherein the
grip member moves from the disengaged position to the engaged
position when the traveler moves rearward from a forward
position.
5. The bone fixation instrument as recited in claim 4, wherein the
movable grip member is biased toward the engaged position and
engages the body so as to prevent the movable grip member from
moving from the disengaged position to the engaged position when
the traveler is in the forward position.
6. The bone fixation instrument as recited in claim 5, wherein when
the traveler moves rearward from the forward position, the movable
grip member becomes disengaged from the body and is biased to the
engaged position.
7. The bone fixation instrument as recited in claim 1, wherein the
tension limiter comprises a spring member connected between the
actuator and the traveler, wherein movement of the actuator causes
the spring member to flex and bias the traveler rearward under a
biasing force.
8. The bone fixation instrument as recited in claim 7, wherein the
traveler moves rearward when the biasing force is greater than the
tension in the bone fixation member.
9. The bone fixation instrument as recited in claim 8, wherein the
traveler remains stationary when the biasing force is not greater
than the tension in the bone fixation member.
10. The bone fixation instrument as recited in claim 7, further
comprising a force transfer member coupled between the actuator and
the spring member, wherein movement of the actuator moves the force
transfer member to flex the spring member.
11. The bone fixation instrument as recited in claim 10, wherein
the spring member is coupled to a movable spring seat that is
connected to the force transfer member.
12. The bone fixation instrument as recited in claim 7, wherein the
spring compresses as the actuator moves from the initial position
toward the tension position, and the compression of the spring
causes the spring to bias the traveler to move rearward.
13. The bone fixation instrument as recited in claim 7, wherein the
actuator is movable from the initial position to a second position
that causes the spring to flex to a position that biases the
traveler rearward and causes the grip to secure to the bone
fixation member prior to increasing the tension in the bone
fixation member.
14. The bone fixation instrument as recited in claim 1, wherein the
actuator is movable from a the initial position to a second
position that causes the grip to secure to the bone fixation
member, and from the second position to the tension position that
causes the traveler to move and increase the tension in the bone
fixation member.,
15. The bone fixation instrument as recited in claim 14, wherein
the actuator moves from the initial position to the second position
to the tension position in one continuous motion.
16. The bone fixation instrument as recited in claim 1, further
comprising a cutter assembly configured to move from a disengaged
position to an engaged position, whereby the cutter assembly cuts
the free end of the bone fixation member when in the engaged
position.
17. The bone fixation instrument as recited in claim 1, further
comprising a safety mechanism that prevents the cutter assembly
from moving from the disengaged position to the engaged position
when the traveler has moved rearward so as to increase tension in
the bone fixation member.
18. The bone fixation instrument as recited in claim 17, further
comprising a second safety mechanism that prevents the actuator
from moving to the tension position when the cutter assembly is in
the engaged position.
19. A bone fixation instrument configured to apply tension to a
bone fixation member about a target bone, the fixation instrument
comprising: a tension assembly configured to secure the fixation
instrument to a free end of the bone fixation member, and further
configured to pull the free end so as to increase tension in the
bone fixation member about the target bone while the tension in the
bone fixation member is less than a select tension, wherein the
tension assembly is unable to further increase tension in the bone
fixation member once the tension in the bone fixation member has
reached the select tension; and a cutter assembly that is
configured to cut the free end of the bone fixation member.
20. The bone fixation instrument as recited in claim 19, further
comprising a safety mechanism that prevents the cutter assembly
from cutting the free end of the bone fixation member while the
tension assembly is increasing tension in the bone fixation
member.
21. The bone fixation instrument as recited in claim 20, wherein
the tension assembly further comprises a grip that is configured to
move from 1) a disengaged position wherein the grip is configured
to loosely receive the free end of the bone fixation member to 2)
an engaged position wherein the grip secures the free end of the
bone fixation member to the bone fixation instrument.
22. The bone fixation instrument as recited in claim 21, wherein
the safety mechanism allows the cutter assembly to cut the free end
of the bone fixation member when the grip is in the engaged
position.
23. The bone fixation instrument according to claim 20, wherein the
cutter assembly is configured to move from a disengaged position to
an engaged position, and further comprising a second safety
mechanism that prevents the tension assembly from increasing
tension in the bone fixation member when the cutter assembly is in
an engaged position.
24. A bone fixation system comprising: at least one bone fixation
member including a strap and a locking mechanism, wherein the strap
can be pulled through the locking mechanism along a first direction
so as to form a loop about a target bone, and the locking mechanism
prevents the strap from moving therethrough along a second
direction opposite the first direction, wherein the strap defines a
free end that extends out the locking mechanism; and a bone
fixation instrument configured to apply tension to the loop about
the target bone, the fixation instrument including: a tension
assembly configured to secure the free end to the fixation
instrument, and further configured to pull the free end so as to
increase tension in the loop while the tension in the loop is less
than a select tension, wherein the tension assembly is unable to
further increase tension in the bone fixation member once the
tension in the bone fixation member has reached the select tension;
and a cutter assembly that is configured to cut the free end of the
bone fixation member so as to separate the free end from the
loop.
25. The bone fixation system according to claim 24, wherein the
cutter assembly is configured to move from a disengaged position to
an engaged position, and further comprising a safety mechanism that
prevents the tension assembly from increasing tension in the bone
fixation member when the cutter assembly is in an engaged position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Ser. No.
13/019,907, filed Feb. 2, 2011, the entire contents of which are
incorporated herein by reference.
BACKGROUND
[0002] In order to provide access to certain internal anatomy, such
as the heart during an open heart procedures, midline sternotomies
are typically performed. A midline sternotomy creates a cut
substantially along the midline of the sternum, thereby dividing
the ribcage into two halves and allowing the surgeon to move the
ribcage so as to provide access to the heart. Upon completion of
the open heart procedure, it is desired to approximate and compress
the sternum, and rigidly maintain the sternal halves in their
approximated position relative to each other so that the sterna
halves are prevented from moving with respect to each other to
promote bone fusion in the weeks following the surgical
procedure.
[0003] During normal anatomical function, for instance during
respiration, body movement, and carrying of objects, forces can be
generated that act on the sternum. One conventional system sternal
fixation assembly includes stainless steel wires that are placed
either parasternally (around the sternum) or transsternally
(through the sternum bone) using a cutting needle that is attached
to the wire, and subsequently twisted to tighten the wire against
the sternum. However, the twisting generates tensile forces onto
the wires that tend to weaken the wire, which can result in
breakage both during the closure or post-operatively. Furthermore,
this type of system relies on the experience of the surgeon when
tightening the wires. If the wires are not tightened enough, the
sternal compression can be compromised. If the wires are tightened
too much, the wire can cut into or through the sternum and/or can
break.
SUMMARY
[0004] In accordance with one embodiment, a bone fixation
instrument is configured to apply tension to a bone fixation member
so as to tighten the bone fixation member about a target bone. The
bone fixation instrument includes a body that defines a front end
and an opposed rear end, a grip configured to secure a free end of
the fixation member to the fixation instrument, a traveler that is
connected to the grip such that the grip moves rearward along with
the traveler so as to increase tension in the bone fixation member,
and an actuator operatively coupled to the traveler. The actuator
can be configured to move from an initial position toward a tension
position in response to an applied force, thereby biasing the
traveler to move rearward. The bone fixation instrument can further
include a tension limiter connected between the actuator and the
traveler. The tension limiter allows the traveler to move rearward
when the tension in the bone fixation member is less than the
selected tension, and prevents the traveler from moving rearward
when the tension in the bone fixation member reaches the selected
tension.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The foregoing summary, as well as the following detailed
description of the preferred embodiments of the application, will
be better understood when read in conjunction with the appended
drawings. For the purposes of illustrating the present disclosure,
there is shown in the drawings preferred embodiments. It should be
understood, however, that the application is not limited to the
specific embodiments and methods disclosed, and reference is made
to the claims for that purpose. In the drawings:
[0006] FIG. 1 is a perspective view of a bone fixation instrument
constructed in accordance with one embodiment;
[0007] FIG. 2A is a perspective view of a bone fixation member
including a body and a locking member, showing the bone fixation
member in an initial configuration;
[0008] FIG. 2B is an enlarged perspective view of a portion of the
bone fixation member illustrated in FIG. 2A, showing the body
inserted through the locking member so as to secure the bone
fixation member about an underlying bone;
[0009] FIG. 3A is a perspective view of a plurality of the bone
fixation members illustrated in FIG. 2A shown tightened about a
target bone and cut;
[0010] FIG. 3B is a perspective view of the bone fixation
instrument illustrated in FIG. 1 operatively coupled to and
tightening one of a plurality of the bone fixation members
illustrated in FIG. 3A;
[0011] FIG. 3C is a perspective view of the bone fixation
instrument illustrated in FIG. 1 operatively coupled to and cutting
one of the tightened bone fixation members illustrated in FIG.
3B;
[0012] FIG. 4 is a perspective view of the bone fixation instrument
illustrated in FIG. 1, with portions removed to illustrate internal
components including a tension assembly and a cutter assembly;
[0013] FIG. 5A is a perspective view of the bone fixation
instrument illustrated in FIG. 4, showing the cutter assembly in a
cutting position;
[0014] FIG. 5B is a perspective view of a front end of the bone
fixation instrument as illustrated in FIG. 5A;
[0015] FIG. 6 is a perspective view of a rear end of the bone
fixation instrument illustrated in FIG. 4;
[0016] FIG. 7A is a perspective view of the front end of the bone
fixation instrument illustrated in FIG. 4, showing the tension
assembly in a disengaged position;
[0017] FIG. 7B is a perspective view of the distal end of the bone
fixation instrument illustrated in FIG. 7A having portions removed
and showing the tension assembly in an engaged position;
[0018] FIG. 8A is a side elevation view of the bone fixation
system, including the bone fixation instrument illustrated in FIG.
4 showing the bone fixation member as illustrated in FIG. 3A, with
the target bone removed for the purposes of illustration, shown
loosely received in the bone fixation instrument with the tension
assembly in the disengaged position;
[0019] FIG. 8B is a side elevation view of the bone fixation system
illustrated in FIG. 8A, showing the tension assembly in the engaged
position such that the bone fixation instrument is secured to the
bone fixation member;
[0020] FIG. 8C is a side elevation view of the bone fixation system
illustrated in FIG. 8B, showing the tension assembly in a tightened
position;
[0021] FIG. 8D is a side elevation view of the bone fixation system
illustrated in FIG. 8C, showing the tension assembly in a
disengaged position after having been previously in the tightening
position FIG. 8C;
[0022] FIG. 8E is a side elevation view of the bone fixation system
illustrated in FIG. 8D, showing the operation of a tension limiter
whereby actuation of the tension assembly toward the tightened
position does not tighten the received bone fixation member;
[0023] FIG. 9 is a side elevation view of the bone fixation system
illustrated in FIG. 8D, but showing actuation of the cutter
assembly;
[0024] FIG. 10 is a perspective view of a bone fixation instrument
similar to the bone fixation instrument illustrated in FIG. 4, but
constructed in accordance with an alternative embodiment;
[0025] FIG. 11 is a side elevation view of the bone fixation system
constructed in accordance with another embodiment, showing both the
tension assembly in a disengaged position, and further showing the
cutter arm in a disengaged position;
[0026] FIG. 12A is a perspective view of the bone fixation system
shown in FIG. 11;
[0027] FIG. 12B is a magnified portion of FIG. 12A, taken along
line 12B;
[0028] FIG. 13 is a side elevation view of the bone fixation system
shown in FIG. 11, showing the tension assembly in a tightened
position and the cutter arm in the disengaged position;
[0029] FIG. 14 is a side elevation view of the bone fixation system
shown in FIG. 11, showing the tension assembly in a partially
engaged position and the cutter arm in an engaged position, and
further showing the safety mechanism in an engaged position so as
to prevent the tension assembly from moving to the tightened
position;
[0030] FIG. 15A is a perspective view of the bone fixation system
shown in FIG. 14; and
[0031] FIG. 15B is a magnified portion of the bone fixation system
shown in FIG. 15A, taken along line 15B.
DETAILED DESCRIPTION
[0032] Certain terminology is used in the following description for
convenience only and is not limiting. The words "right", "left",
"lower" and "upper" designate directions in the drawings to which
reference is made. The words "proximally" and "distally" refer to
directions toward and away from, respectively, the surgeon using
the surgical instrument. The words, "anterior", "posterior",
"superior", "inferior" and related words and/or phrases designate
preferred positions and orientations in the human body to which
reference is made and are not meant to be limiting. The terminology
includes the above-listed words, derivatives thereof and words of
similar import.
[0033] Referring to FIGS. 1-3B, a bone fixation assembly 20
includes a bone fixation instrument 22 and at least one bone
fixation member 24 such as a plurality of bone fixation members 24
that are configured to secure a first and second bone segments 26a
and 26b of a target bone 28, such as a sternum, that are separated
at a fracture location 30 together in a compressed approximated
position.
[0034] In accordance with the illustrated embodiment, each bone
fixation member 24 can be substantially configured as a cable tie,
and can include a flexible strap 32 defines a strap body 33 and has
first end 34a and a second end 34b opposite the first end 34a along
the length of the strap 32, a needle tip 36 that extends from the
first end 34a, and a locking mechanism 38 that extends from the
second end 34b. The strap 32 can be made from any suitable
biocompatible material as desired, such as PEEK.
[0035] Each bone fixation member 24 can further include a first
initiation region 40 that extends from the first end 34a toward the
second end 34b along a portion of a length of the strap 32 (for
instance, approximately 1/3 the length of the strap 32) and a
second locking region 42 that extends between the first initiation
region 40 and the second end 34b. In accordance with the
illustrated embodiment, the second locking region 42 extends from
the first initiation region 40 to the second end 34b. The first
initiation region 40 can include a plurality of small protrusions
that extend out from the strap body 33 and alternate with recessed
regions disposed between adjacent protrusions. Alternatively, the
initiation region 40 can be substantially smooth and devoid of
protrusions or teeth. The second locking region 42 can include a
plurality of locking teeth 48 that extend out from the strap body
33 a distance greater than the protrusions and are separated by
recessed regions 51 disposed between adjacent locking teeth. It
should be appreciated that the locking region 42 can extend along
any portion up to all of the strap body 33 as desired.
[0036] The locking mechanism 38 includes a housing 50 a strap
receiving slot 52 that extends through the housing 50 and is
configured to receive the first end 34a of the strap 32. In
accordance with the illustrated embodiment, the first end 34a is
inserted through the slot 52 so as to define a loop 55 about the
target bone 28. The locking mechanism 38 is configured to allow the
strap 32 to translate unidirectionally through the slot 52 along
the direction of Arrow A so as to reduce the size of the loop 55
about the first and second segments 26a and 26b of the target bone
28. For instance, the needle tip 36 can be inserted through the
slot 52 and subsequently removed, for instance by cutting a neck 56
of the strap body 33 that defines reduced thickness at a location
adjacent the needle tip 36, such that the strap 32 remains in the
slot 52. In accordance with the illustrated embodiment, the locking
mechanism 38 includes a locking member such as a tongue 54 that is
connected to the housing 50 and includes at least one complementary
tooth such as a plurality of locking teeth 58 that extend into the
slot 52. The locking teeth 58 define a beveled leading edge 60 that
that is configured to cam over complementary beveled leading edges
49 of the locking teeth 48 when the strap 32 is translated through
the slot 52 along the direction of Arrow A. The locking teeth 58
and 48 further define trailing edges 62 and 47 that are sloped less
than the beveled leading edges 60, such that the trailing edges 62
and 47 engage to prevent the strap 32 from translating through the
slot 52 along the direction opposite Arrow A, which would increase
the size of the loop 55.
[0037] During operation, the strap 32 is wrapped around the first
and second segments 26a and 26b of the target bone 28, and the
needle tip 36 is inserted through the slot 52 and pulled through
the slot 52 so as to cause the strap 32 to subsequently translate
through the slot 52. The needle tip 36 can be removed from the
strap 32, and the strap 32 can then be further pulled, for instance
manually, through the slot 52. As the strap 32 is translated
through the locking mechanism 38 along the direction of Arrow A,
the small protrusions of the initiation region 40 can slide through
the slot 52 without engaging the locking teeth 58 of the locking
mechanism 38. As the locking region 42 of the strap 32 is
translated through the slot 52 along the direction of Arrow A, the
locking teeth 48 and 58 can engage to prevent the tension that is
induced in the strap 32 from causing the strap 32 to back out of
the slot 52 along a direction opposite Arrow A. For instance, as
the strap 32 translates through the locking mechanism 38 along the
direction of Arrow A, the size of the loop 55 about the target bone
28 decreases until tactile feedback indicates that tension has been
induced in the strap 32.
[0038] As illustrated in FIG. 3B, the fixation instrument 22
includes a tension assembly 70 that is configured to secure the
fixation instrument 22 to the strap 32, and is further configured
to further pull the strap 32 through the locking mechanism 38
thereby further inducing tension in the strap 32 until the strap 32
has securely compressed the bone first and second bone segments 26a
and 26b of the target bone 28 together at the fracture location 30.
As illustrated in FIG. 3C, the fixation instrument 22 further
includes a cutter assembly 72 that is configured to cut a free end
35 of the strap 32 that has passed through the locking mechanism 38
once a desired tension has been induced in the strap 32 about the
first and second segments 26a and 26b of the target bone 28. For
instance, the desired tension can be within a range defined by and
between a lower end that can be approximately 50 Newtons or
approximately 80 Newtons, and an upper end that can be
approximately 150-160 Newtons or 200 Newtons. It should be
appreciated that the desired tension can depend on the bone quality
and the preference of the surgeon, and can for instance be any
tension as desired that reliably secures the target bone 28 without
overtightening the strap 32.
[0039] Referring now to FIGS. 1 and 4, the fixation instrument 22
includes a body 76 that defines a front end 78a and an opposed rear
end 78b spaced from the front end 78a along a longitudinal
direction L and opposed sides 80 that are spaced along a lateral
direction A that is substantially perpendicular with respect to the
longitudinal direction L. The fixation instrument 22 further
includes a handle 82 that is supported by the body 76, and can
extend down from the body 76 along a transverse direction that is
substantially perpendicular with respect to both the longitudinal
direction L and the lateral direction A. In accordance with the
illustrated embodiment, the transverse direction T is oriented
vertically, and the longitudinal and lateral directions L and A are
oriented horizontally, though it should be appreciated that the
orientation of the fixation instrument may vary during use. In
accordance with the illustrated embodiment, the body 76 is elongate
in the longitudinal direction L.
[0040] The fixation instrument 22 further includes a trigger 84
that extends down from the body 76 at a location spaced forward
from the handle 82, and a nose 86 disposed at the front end 78a of
the body 76. The handle 82, the trigger 84, and the nose 86 can be
discreetly attached to the body 76 or integral with the body 76 as
desired. The body 76 can include an outer housing 88 that includes
a pair of housing members 90a and 90b that are laterally opposed
and define respective outer sides 92 and can be joined together via
fasteners such as screws 94 so as to support the various internal
components of the fixation instrument 22.
[0041] It should be appreciated that the body 76 of the fixation
instrument 22 can be constructed in any suitable manner as desired.
For instance, as illustrated in FIG. 1, the outer housing members
90a and 90b can include a flange 93 that extends laterally inward
toward each other from the sides 80 at a forward location of the
body 76. Alternatively, as illustrated in FIG. 10, the flange 93
can extend further rearward and terminate adjacent an actuator
100.
[0042] Furthermore, referring to FIGS. 11-15, the fixation
instrument can include an outer housing 188 that can be constructed
as described above with respect to the outer housing 88, or can be
constructed in accordance with any suitable alternative embodiment.
For instance, as illustrated in FIGS. 11-15, the outer housing 188
can include first and second housing members 190a and 190b that are
spaced apart from each other along the lateral direction A. The
outer housing 188 can further include at least one spacer member
such as a plurality of spacer members 145, 147, and 149 that are
disposed between the first and second housing members 190a and
190b. The fixation instrument 22 can further include one or more
fasteners, such as screws 94, that attach the first and second
housing members 190a and 190b to the spacer members 145, 147, and
149. For instance, the screws 94 can pass partially through the
spacer members 145, 147, and 149, or may extend from one or both of
the first and second housing members 190a and 190b, completely
through the spacer members 145, 147, and 149, and all the way to
the laterally opposed one of the first and second housing members
190a and 190b. The number of spacers, their respective geometric
configurations, and the locations at which spacers are respectively
positioned between housing members 190a and 190b may vary among
different embodiments, as long as each parameter is suitable for
providing adequate structural support for housing members 190a and
190b.
[0043] In accordance with the illustrated embodiment, the spacer
member 145 can be disposed at a distal end of the handle 82. While
the spacer member 145 is shown as a unitary part, in other
embodiments the spacer 145 may be assembled, for example, from two
laterally opposing halves that are mated together. Furthermore, in
accordance with the illustrated embodiment, the spacer member 147
is disposed at a location that extends from the base of handle 82
rearward to along longitudinal direction L towards rear end 78b of
body 76. The spacer member 147 can further include a tail 151 that
is disposed at a portion of spacer 147 that is adjacent to the base
of handle 82 and distal to rear end 78b of body 76, and further
includes an elongate portion 153 that can extend rearward from the
tail 151. The tail 151 can extend an angle that is offset from a
longitudinally elongate portion 153 towards the distal end of
handle 82. For example, the tail 151 can define a direction of
elongation that is angularly offset from a direction of elongation
of the elongate portion 153, which can be defined by the
longitudinal direction L, so as to define an angle between the
direction of elongation of the tail 151 and the direction of
elongation of the elongate portion 153, and thus the longitudinal
direction L, of approximately 85 to approximately 95 degrees. While
the spacer member 147 is shown as a unitary part, it should be
appreciated that the spacer member 147 may be assembled, for
example, from two laterally opposing halves that are mated
together.
[0044] The tail 151 and the elongate portion 153 are preferably
formed from a single piece of material, but may alternatively
comprise separate pieces that are bonded, welded, or otherwise
fixedly attached to one another. The spacer member 149 can provide
structural support for portions of the first and second housing
members 190a and 190b that are located between the front end 78a
and the rear end 78b of body 76. The spacer 149 can be assembled,
for example, from two laterally opposing halves that are mated
together during assembly of the body 76, or can alternatively be a
unitary component. When the opposing halves 149a and 149b are mated
together, the opposing halves 149a and 149b can define a channel
155 that extends completely through the spacer 149 along the
longitudinal direction L. When the spacer member 149 comprises a
unitary structure that is not assembled from two laterally opposing
halves, the spacer member 149 likewise defines a channel 155 that
extends completely through the spacer member 149 along the
longitudinal direction L. The channel 155 can define a
cross-sectional dimension, such as a diameter, that can be greater
than a corresponding outer dimension of the longitudinally
extending traveler 98, such that the longitudinally extending
traveler 98 can move within channel 155 along the longitudinal
direction L, and thus towards or away from the front end 78a and
the rear end 78b, respectively, of the body 76. The fixation
instrument 22 can further include at least one safety member, such
as at least one corresponding wing, which can be configured as
first and second laterally opposed flexible wings 161a and 161b
that extend from the outer housing 188. In accordance with the
illustrated embodiment, the spacer member 149 defines a first or
front end 157 and an opposed second or rear end 159. As described
more fully below in connection with FIGS. 11-15, the first and
second wings 161a and 161b can extend from the spacer member 149,
for instance at the rear end 159.
[0045] Returning to embodiments that are illustrated, for example,
in FIGS. 1, 6, and 7A-B, the housing 88 can support the tension
assembly 70 that is configured to tighten the bone fixation member,
thereby inducing tension in the bone fixation member 24, such as
the strap 32, and can further support the cutter assembly 72 that
is configured to remove a free end 35 of the bone fixation member
24 once the tension assembly 70 has induced a desired level of
tension in the bone fixation member 24. The tension assembly 70
includes a grip 96 that is movable between a disengaged position
(FIG. 7A) whereby the grip 96 is configured to loosely receive the
strap 32, such as the portion of the strap that has passed through
the locking mechanism 38, and an engaged position (FIG. 7B) whereby
the grip 96 is configured to be secured to the received strap 32.
The tension assembly 70 further includes a traveler 98 that is
operably coupled to the grip 96 and extends rearward from the grip
96, such that rearward movement of the traveler 98 causes the grip
96 to move rearward in the secured configuration, thereby inducing
tension in the strap 32. The tension assembly 70 can further
include an actuator 100 such as the trigger 84 and a tension
limiter 102 (FIG. 6) connected between the trigger 84 and the
traveler 98. The tension assembly 70 can further include a force
transfer member 104 that is connected between the trigger 84 and
the tension limiter 102, thereby operatively coupling the trigger
84 to the traveler 98.
[0046] During operation, and as described in more detail below, the
free end 35 of the strap 32 is received in the grip 96, the nose 86
is placed against the housing 50 of the locking mechanism 38, and
the actuator 100 is moved from an first initial position to a
second grip position that causes the grip 96 to iterate from the
disengaged position to the engaged position, and is further moved
from the second grip position to a third tension position that
causes the traveler 98 to move rearward, thereby inducing tension
in the strap 32 when the tension in the strap 32 is less than a
select tension, which can be a desired maximum tension as
determined by the tension limiter 102. When the tension in the
strap 32 reaches the maximum tension, the tension limiter 102
prevents the traveler 98 from moving rearward when the actuator 100
is moved to the tension position.
[0047] The cutter assembly 72 includes a cutter arm 106 movably
supported by the body 76 and a cutter blade 108 that is carried by
the cutter arm 106. The cutter arm 106 is movable from a seated
disengaged position (see FIG. 4) whereby the cutter blade 108 is
spaced from the free end 35 of the strap 32 that is received in the
grip 96 to an engaged position (see FIGS. 5A-B) whereby the cutter
blade 108 cooperates with a complementary cutter blade 87 of the
nose 86 so as to cut the free end 35 of the strap 32 (see FIG. 9).
The fixation instrument 22, and in particular the cutter assembly
72, further includes a safety mechanism 110 that moves from a
disengaged position, whereby the cutter arm 106 can move from the
seated disengaged position toward the engaged position, and an
engaged position that prevents the cutter arm 106 from moving from
the seated disengaged position toward the engaged position.
[0048] Referring now to FIGS. 4 and 7A-B, the traveler 98 of the
fixation instrument 22 can be provided as a longitudinally
extending traveler rod 111 that extends forward from the tension
limiter 102 and supports the grip 96 at its front end. The traveler
rod can define a rectangular cross-section as illustrated in FIG.
4, a substantially circular cross section as illustrated in FIG.
10, or any alternative size and shape as desired. The grip 96
includes a first lower grip member 112 and a second upper grip
member 114 spaced from the lower grip member 112 so as to define a
gap 116 disposed between the lower and upper grip members 112 and
114. The lower grip member 112 defines first grip surface 118 that
faces the upper grip member 114, and can further define a plurality
of teeth 120 that extend out from the first grip surface 118 toward
the upper grip member 114. The teeth 120 are configured to assist
in reliably securing the grip 96 to the strap 32. The upper grip
member 114 is supported by the traveler rod 111 and defines a
second grip surface 115 that faces the first grip surface 118. The
first and second grip surfaces 118 and 115 can be sized and shaped
as desired. In accordance with the illustrated embodiment, the
first grip surface 118 is curved and substantially arc-shaped in
accordance with the illustrated embodiment, such that the first
grip surface 118 is convex with respect to the upper grip member
114. Furthermore in accordance with the illustrated embodiment, the
second grip surface 115 is substantially flat.
[0049] The traveler rod 111 defines a forked first front end 117a
that defines a pair of laterally spaced side walls 122. The upper
grip member 114 can be rigidly supported by the traveler rod 111,
and the lower grip member 112 can be pivotally coupled to the
traveler rod 111 at a pivot location 113 about a laterally
extending pivot pin 115 that defines a lateral pivot axis, and can
further be disposed between the side walls 122. The grip 96 can
further include a biasing member such as a torsion spring 124 that
biases the lower grip member to pivot in a forward direction about
the pivot location 113 toward the nose 86 from the disengaged
position of the grip 96 to the engaged position of the grip 96. The
grip surface 118 can extend eccentrically about the pivot location
113 such that the grip surface 118 moves upward toward the upper
grip member 114 as the lower grip member 112 pivots forward to the
engaged position.
[0050] The lower grip member 112 defines a first or forward stop
surface 126 and the nose 86 defines a complementary second or rear
stop surface 127. When the traveler rod 111 is in a forward
position, the grip 96 is in the disengaged position whereby the
torsion spring 124 biases the forward stop surface 126 against the
rear stop surface 127. When the grip is in the disengaged position,
the gap 116 is sized greater than the thickness of the free end 35
of the strap 32 as illustrated in FIG. 7A. Accordingly, the free
end of the strap 35 can be received in the gap 116 between the
first and second grip surfaces 118 and 115 as illustrated in FIG.
8A. As the traveler rod 111 moves rearward, the lower grip member
112 pivots forward about the pivot location 113 such that the grip
surface 118 moves toward the grip surface 115 of the upper grip
member 114 as illustrated in FIG. 7B, thereby reducing the gap 116
until the grip 95 captures the free end 35 of the strap 32 that is
received in the gap 116 between the first and second grip surfaces
118 and 115 under the force of the torsion spring 124 (FIG. 8B). It
should thus be appreciated that as the traveler rod 111 further
moves rearward, the free end 35 of the strap 32 will move rearward
along with the grip 95 and the traveler rod 111.
[0051] Referring now to FIGS. 4 and 6, the traveler rod 111 defines
a second rear end 117b opposite the front end 117a. The rear end
117b of the traveler rod 111 is connected to the tension limiter
102. The tension limiter 102 includes a spring member 128 such as a
helical compression spring that defines a first or front end 130a
and a second or rear end 130b. The spring member 128 is fixed with
respect to movement relative to the traveler rod 111 at its rear
end 130b, and movable with respect to the traveler rod 111 at its
front end 130a. The spring member 128 is further coupled to the
trigger 84 at its front end. Thus, the spring member 128 is coupled
to the trigger 84 at its end that is also movable with respect to
the traveler rod 111 so as to generate a force to the traveler rod
111 that biases the traveler rod rearward away from the locking
mechanism 38 of the bone fixation member 24.
[0052] In accordance with the illustrated embodiment, the tension
limiter 102 includes a stationary end cap 129 that can be threaded
onto or otherwise secured to the traveler rod 111, for instance to
the rear end 117b of the traveler rod 111. The rear end 130b of the
spring member 128 is attached to the end cap 129 so as to secure
the spring member 128 to the traveler rod 111 at its rear end 130b
such that the rear end 130b is fixed with respect to movement
relative to the rod 111. Thus, as the rear end 130b of the spring
member 128 moves rearward, the traveler rod moves rearward along
with the rear end 130b of the spring member 128. The tension
limiter 102 can further include a movable spring seat 132 that is
fixed to the movable front end 130a of the spring member 128. In
accordance with the illustrated embodiment, the traveler rod 111
extends through the spring seat 132, such that the spring seat 132
is movable in the longitudinal direction L along the traveler rod
111. The traveler rod 111 can define a longitudinally elongate slot
134 extending therethrough that can receive a projection of the
spring seat 132. Thus, the slot 134 defines a length that allows
the movable spring seat 132 to translate from its forward-most
position to its rearward-most position.
[0053] The tension assembly 70 further includes the force transfer
member 104 illustrated as a force transfer arm 136 that is
pivotally connected between the movable spring seat 132 and the
trigger 84. Otherwise stated, the movable front end 130a of the
spring member 128 is coupled to the trigger 84 via the force
transfer arm 136. In accordance with the illustrated embodiment,
the force transfer arm 136 defines a front end 138a and an opposed
rear end 138b. The force transfer arm 136 is pivotally coupled, for
instance at its rear end 138b to the spring seat 132 at a pivot
location 139 that defines a lateral pivot axis. The force transfer
arm 136 is further pivotally coupled, for instance at its front end
138a to the trigger 84 at a pivot location 140 that defines a
lateral pivot axis.
[0054] Referring again to FIG. 4, tension assembly 70 further
includes the trigger 84 that includes a lower grip portion 85
extending down from the housing 88 at a location spaced forward of
the handle 82 and an upper securement portion 89 pivotally
connected to the force transfer arm 136 and further pivotally
connected to the housing 88. The trigger 84 defines an aperture 91
that extends longitudinally through the upper securement portion 89
and receives the traveler rod that extends through the aperture,
and thus the upper securement portion 89. The securement portion 89
of the trigger 84 is pivotally connected to the force transfer arm
136 at the pivot location 140, which defines a first lower pivot
location of the trigger 84. The securement portion 89 of the
trigger 84 is further pivotally coupled to the housing 88 at a
second upper pivot location 142 that defines a lateral pivot axis.
The user can grasp the handle 82 and the grip 85 of the trigger 84
with one hand, and squeeze the trigger 84, which causes the trigger
84 to pivot rearward about the second upper pivot location 142.
Because the lower pivot location 140 is disposed between the upper
pivot location 142 and the grip 85, the lower pivot location 140
moves rearward when the trigger 144 is moved rearward by the user.
The tension assembly 70 further includes a spring member 146 that
is connected between the handle 142 and the trigger 144 that biases
the trigger 144 forward to its initial position. The fixation
instrument 22 includes a stop member illustrated as a dowel 148
that extends laterally between the housing members 90a and 90b. The
front edge of the securement portion 89 of the trigger 84 abuts the
dowel 148 so as to locate the trigger 144 in its first initial
position under the force of the spring member 146.
[0055] Operation of the fixation instrument will now be described
with further reference to FIGS. 8A-E. For instance, as illustrated
in FIGS. 7A and 8A, the trigger 84, and thus the tension assembly
70, is in a first initial position whereby the front end 117a of
the traveler rod 111 is disposed adjacent and proximate to the nose
86, such that the forward stop surface 126 of the lower grip member
112 abuts the complementary rear stop surface 127 of the nose 86,
thereby causing the gap 116 to define a transverse thickness
greater than that of the free end 35 of the strap 32. The free end
35 is inserted into the gap 116 and the nose 86 is positioned so as
to abut the locking mechanism 38. The nose 86 thus provides a brace
member that prevents the locking mechanism 38 from traveling
rearward when the fixation instrument 22 applies a rearward force
to the free end 35.
[0056] When the tension assembly 70 is in the first initial
position, the spring member 128 can be in an initial position that
can be a neutral position, or the movable spring seat 132 can be
disposed at a forward location with respect to the neutral position
such that the initial position of the spring member 128 can be
flexed, such as slightly extended, from its neutral position. For
instance, the force of the spring member 146 that biases the
trigger 84 forward can be greater than the force of the spring
member 128 that biases the trigger 84 rearward when the movable
spring seat 132 is displaced forward from its neutral position.
When the spring member 128 is extended from its neutral position,
the spring member can apply a rearward compressive force onto the
end cap 129, and thus the traveler rod 111, which biases the lower
grip member 112 forward against the nose 86. It is appreciated that
the torsion spring 124 that biases the lower grip member 112
forward against the nose 86 creates an equal and opposite force
against the traveler rod 111 that biases the traveler rod
rearwards. Thus, the forward force of the spring member 128 applied
to the traveler rod 111 when the spring member 128 is slightly
extended is greater than the rearward biasing force of the torsion
spring 124 against the traveler rod 111. Because the forward
biasing force of the spring member 128 is greater than the rearward
biasing force of the torsion spring 124 when the spring member 128
is slightly extended, the spring member 128 can actively
maintaining the grip 96 in its disengaged position.
[0057] Alternatively, the movable spring seat 132, and thus, the
spring member 128, can be in a neutral position when the tension
assembly 70 is in the first initial position, such that the spring
member 128 does not apply a forward biasing force or a rearward
biasing force to the traveler rod 111. As described above, the
torsion spring 124 can apply a force to the traveler rod 111 that
biases the traveler rod rearwards 111. However, rearward movement
of the traveler rod 111 would cause the rear end 130b of the spring
member 128 to move away from the front end 130a of the spring
member 128, thereby causing the spring member 128 extend from its
neutral position. The spring member 128 can have an spring constant
that is greater than the spring constant of the torsion spring 124
such that the spring member 128 resists extension under the forces
of the torsion spring 124, and thereby passively maintains the
lower grip member 112 in its disengaged position whereby the
forward stop surface 126 rests against the complementary rear stop
surface 127 of the nose 86 and the gap 116 is thus thicker in the
transverse direction T than the free end 35 of the strap 32 that is
received in the gap 116.
[0058] Referring now to FIGS. 4 and 8B, when the user applies an
actuation force, such as a rearwardly directed force F, to grip
portion 85 of the trigger 84, the trigger 85 and thus also the
tension assembly 70 moves from the first initial position to the
second grip position that causes the grip 96 to iterate from the
disengaged position to the engaged position. In accordance with the
illustrated embodiment, the rearward force applied to the grip
portion 85 of the trigger 84 causes the trigger 84 to pivot
rearward about the upper pivot location 142, which causes the lower
pivot location 140 to move rearward. It should be appreciated that
the lower pivot location 140 moves rearward about an arc-shaped
travel path about the upper pivot location 142. Rearward movement
of the lower pivot location 140 causes the force transfer arm 136
to likewise moves rearward, thereby transferring the force from the
trigger to the movable spring seat 132 and the front end 130a of
the spring member 128. It should be appreciated that the force
transfer arm 136 pivots relative to the trigger 84 about the lower
pivot location 140 as the force transfer arm 136 moves
rearward.
[0059] As the force transfer arm 136 moves rearward, the force
transfer arm 136 further causes the movable spring seat 132 and the
front end 130a of the spring member 128 to translate rearward along
the travel rod 111 in the longitudinal direction L toward the rear
end 130b of the spring member 128, thereby flexing the spring
member 128 from the first initial position. It should be
appreciated that the force transfer arm 136 pivots relative to the
movable spring seat 132 about the pivot location 139. As the front
end 130a of the spring member 128 moves rearward toward the rear
end 130b of the spring member 128, the spring member 128 flexes
from its neutral position so as to apply a rearward biasing force
to the traveler rod 111. In accordance with the illustrated
embodiment, the spring member 128 compresses when the end 130a of
the spring member 128 moves rearward, and thus biases the end 130b,
the end cap 129, and also therefore the traveler rod 111 to move
rearward. Alternatively, the movement of the end 130a of the spring
member 128 can be sufficient so as to reduce the force of the
spring 128 that biases the traveler rod 111 to a level that is less
than the force of the torsion spring 124 that biases the traveler
rod 111 rearward. The fixation instrument 22 can define an aperture
119 that extends through the rear end 78b of the body 76. The
aperture 119 is sized to receive the end cap 129 such that the end
cap 129 can extend beyond the housing 88 due to rearward travel of
the rear end 130b of the spring member 128.
[0060] Accordingly, referring also to FIGS. 7A-B, the traveler rod
111 is biased, under a biasing force applied by the torsion spring
124, the spring member 128, or both to move rearward away from the
nose 86. As the rod 111 moves away from the nose 86, the torsion
force of the torsion spring 124 causes the lower grip member 112 to
pivot forward about the pivot location 113 along the direction of
Arrow B so as to reduce the gap 116 until the grip surfaces 118 and
115 capture the free end 35 of the strap 32 in the gap 116, thereby
securing the free end 35 to the fixation instrument 22 while the
nose 86 abuts the loop 55, and in particular the housing 50 of the
locking mechanism 38. Thus, it can be said that moving the trigger
84 from the first neutral position to the second neutral position
causes the grip 96 to iterate from its disengaged position to its
engaged position.
[0061] Referring now to FIGS. 4, 6, and 8C, continuous application
of the force F to the grip portion 85 of the trigger 84 causes the
trigger 84 to further pivot about the upper pivot location 142,
thereby causing the trigger 84, and thus the tension assembly 70,
to move from the second grip position to a third tension position
that causes the traveler 98 to move rearward, thereby applying
tension to the free end 35 of the strap 32 when the tension in the
strap 32 is less than the desired tension, such as a maximum
tension as determined by the tension limiter 102. Because
engagement of the nose 86 of the fixation instrument 22 with the
loop 55, and in particular the housing 50 of the locking mechanism
38, provides a brace that prevents the loop 55 from moving rearward
along with the free end 35, when the tension assembly 70 places the
free end 35 in tension, the strap 32 and in particular the locking
region 42 is further pulled through the locking mechanism 38. As
described above with reference to FIG. 2B, the locking teeth 58 and
48 engage so as to allow the locking region 42 to be pulled through
the locking mechanism so as to reduce the size of the loop 55 or to
place the loop 55 in further tension about the bone segments that
are disposed in the loop 55. Whether the size of the loop 55 is
reduced or whether the loop 55 is further tightened about the bone
segments disposed in the loop, it can be said that the fixation
instrument places the bone fixation member 24 in tension when the
tension assembly moves from the second grip position to the third
tension position.
[0062] Accordingly, once a trigger stroke has been completed
whereby the trigger 84 has been moved to its rearward-most position
as illustrated in FIG. 8C, the user can release the trigger 84
which causes the spring member 146 to bias the trigger 84 to its
forward position shown in FIG. 8D. Once the trigger 84 has moved to
its forward position, the trigger 84 and thus the tension assembly
70 are in the first initial position, such that the lower grip
member 112 is biased against the nose 86 thereby placing the grip
96 in its disengaged position as described above. Accordingly,
while the free end 35 of the strap 32 is no longer secured to the
fixation instrument 22, the engagement of the locking teeth 58 and
48 prevent the increased tension induced in the loop 55 from
allowing the free end 35 to move through the housing in a direction
opposite Arrow A that would reduce the tension in the loop 55.
[0063] It should be appreciated that the motion of the trigger 84
from the second grip position to the third tension position can be
a continuation of the movement from the first initial position to
the second grip position. Thus, the trigger 84 can move from the
first initial position to the second grip position to the third
tension position in a single fluid motion.
[0064] The nose 86 can again be placed in contact with the locking
mechanism 38 and the free end 35 can be received in the gap 116 of
the grip 96, and the tension assembly 70 can be iterated from the
first initial position to the second grip position to the third
tension position as many times as desired, for instance until the
tension induced in the loop 55 reaches a predetermined maximum
tension. When the tension in the loop 55 reaches the maximum
tension, the tension limiter 102 prevents the traveler 98 from
moving rearward when the actuator 100 is moved to the tension
position.
[0065] For instance, referring now to FIGS. 4, 6, and 8E, it should
be appreciated that the spring member 128 has a spring constant
that is configured to apply a predetermined biasing force to the
traveler rod 111 when the front end 130a of the spring member 128
has translated rearward a distance corresponding to full rearward
actuation of the trigger 84. Accordingly, so long as the tension in
the loop 55 is less than the desired force as defined by the spring
member 128 and length of travel of the front end 130a of the spring
member 128, compression of the spring member 128 will cause the
force applied by the spring member 128 to move the traveler rod 111
rearwards. However, once the tension induced in the loop 55 reaches
the desired force, compression of the spring member 128 due to
rearward movement of the front end 130a will cause the spring
member 128 to apply a rearward biasing force against the traveler
rod 111 that is insufficient to overcome the force necessary to
further tighten the loop 55.
[0066] It should appreciated that the spring member 128 can be
configured to apply a rearward biasing force against the traveler
rod 111 that is greater than the tension induced in the loop 50
about the target bone 28. For instance, the spring member 128 can
apply a force that is sufficient to overcome both the tension of
the loop 50 and the additional force that causes one or both of the
locking teeth 48 and 52 to deflect as the teeth ride over each
other when tightening the loop 55. Accordingly, the tension limiter
102 can be configured apply a force that is greater than, but
corresponds to, the tension in the loop 55 about the target bone.
Thus, the maximum force applied by the tension limiter 102 can
correspond to the maximum desired tension in the loop 55, it being
appreciated that once the teeth 48 and 52 ride over and past each
other, the tension in the loop 55 can decrease somewhat as the
teeth 48 and 52 interlock. In accordance with one embodiment, the
tension limiter 102 can apply a maximum force as desired, for
instance up to approximately 430 Newtons or any other force as
desired that corresponds to a desired maximum tension in the loop
55 about the target bone 28. As a result, once the desired maximum
tension in the loop 55 has been induced about the target bone 28,
the force applied by the tension limiter 102 when the trigger 84 is
fully actuated is insufficient to cause the teeth 48 and 58 to ride
past each other and further tighten the loop 55. Accordingly, once
the maximum tension in the loop 55 has been induced about the
target bone 28, the force applied by the tension limiter 102 will
be insufficient to cause the traveler rod 111 to translate rearward
a sufficient distance that further tightens the loop 55 about the
target bone 28.
[0067] It should be appreciated that the spring member 128 can
alternatively be configured as an extension spring. For example, in
accordance with an alternative embodiment, the front end 130a can
be connected to the traveler rod 111 and fixed with respect to the
traveler rod 111, and the rear end 130b can be movable relative to
the traveler rod 111. For instance, the rear end 130b can be
coupled to the trigger 84 via the force transfer member 104 in the
manner described above. The tensile force applied to the rear end
130b and corresponding rearward displacement of the rear end 130b
can thus cause the spring force to bias the traveler rod 111 to
move rearward, thereby inducing tension in the strap 32 in the
manner described above. Thus, the initial position of the spring
member 128 initial position that can be a neutral position as
described above, or the initial position of the spring member 128
can be flexed, such as slightly compressed, from its neutral
position.
[0068] Referring now to FIGS. 4-5B, the fixation device 22 includes
a cutter assembly 72 that includes a cutter arm 106 having a front
end 107a and a rear end 107b, and a movable cutter blade 108
carried by the cutter arm 106, for instance at the front end 107a.
The cutter arm 106 can be sized and shaped as desired, and is
constructed in accordance with the illustrated embodiment such that
the front and rear ends 107a and 107b extend substantially
longitudinally. The cutter arm 106 can also include an offset
segment 107c that extends laterally outward along a forward
direction from the rear end 107b toward the front 107a. Thus, the
front end 107a can be offset laterally outward with respect to the
rear end 107b. For instance, the rear end 107b can be disposed
between the opposed sides 80 and the front end 107a can be coupled
to one of the side 80 at a location laterally outward of the side
80. The cutter arm 106 can further include an intermediate
longitudinal segment 107d that extends forward from the offset
segment 107c and is thus extends substantially parallel to the
front and rear ends 107a and 107b. The cutter arm can also include
a transversely offset segment 107e that extends between the
intermediate longitudinal segment 107d and the front end 107a, and
extends transversely down along a forward direction. Accordingly,
the front end 107a can be transversely offset with respect to the
rear end 107b. The cutter arm 106 can further include a grip 150 at
disposed at the rear end 107b.
[0069] Referring also to FIG. 6, the cutter assembly 72 can include
a seat 158 that receives the cutter arm 106 at an upper end of the
body 76 when the cutter arm 106 is in its disengaged position. In
accordance with the illustrated embodiment, the seat 158 is sized
and shaped so as to receive the cutter arm 106. Accordingly, when
the cutter arm 106 is seated in the seat 158, the cutter arm 106
can be said to be in a seated disengaged position. The seat 158 can
further include at least one retainer member 162, such as a pair of
laterally opposed retainer members 162 that are spaced apart a
distance slightly less than the lateral thickness of the cutter arm
106. The retainer members 162 can be spring loaded to the position
spaced apart a distance slightly less than the lateral thickness of
the cutter arm 106. For instance, the cutter arm 106 can define a
recess 164 that is sized to receive the retainer members 162 when
the cutter arm 106 is in its seated disengaged position.
Accordingly, when moving the cutter arm 106 to and from its seated
disengaged position, an engagement force along the direction of
Arrow C can be applied to the cutter arm 106 that is sufficient to
overcome the retention force of the retainer members 162, which
causes the retainer members 162 to pop out of the recess 164 and
free the cutter arm 106 from the seat 158.
[0070] Referring also to FIGS. 7A-B, the cutter arm 106 can be
pivotally attached to the body 76, for instance at one of the sides
80. In accordance with the illustrated embodiment, the cutter arm
106 is pivotally attached at its front end 107a to the nose 86 at a
pivot location 152 that defines a lateral pivot axis. For instance,
the cutter assembly 72 can include a blade support body 154 that is
substantially cylindrical and extends through a side wall of the
nose 86 and rotatable about its central axis so as to allow the
cutter arm 106 to pivot between its engaged position and its
disengaged position. When the cutter arm 106 is in its disengaged
position, the cutter blade 108 is spaced above a complementary and
substantially stationary cutter blade 87 of the nose 86 so as to
define a gap 156 that has a transverse dimension greater than that
of the free end 35 of the strap 32 so that the free end 35 is
loosely received in the gap 156, which is disposed forward with
respect to the grip 96, and thus the gap 116.
[0071] Referring again to FIGS. 5A-B, the cutter arm 106 can be
pivoted up and forward about the pivot location 152 along the
direction of Arrow C to its engaged position, which causes the
cutter blade 108 to travel down along an arc-shaped path toward the
complementary cutter blade 87 so as to reduce the size of the gap
156. The cutter blade 108 is recessed rearward with respect to the
complementary cutter blade 87 such that the cutter blade 108 slides
past the cutter blade 87. Accordingly, the cutter blades 108 and 87
cooperate so as to cut the free end 35 of the strap 102 that is
received in the gap 156 as the cutter blade 108 slides past the
cutter blade 87 (see FIG. 9). Accordingly, when the nose 86 abuts
the locking mechanism 38 of the bone fixation member 24 such that
the gap 156 is aligned with the outlet end of the strap-receiving
slot 52 of the housing 50 of the locking mechanism (see FIGS. 2B
and 3C) and the arm 106 is moved to its engaged position, the
cutter assembly 72 can cut the free end 35 at a location that is
spaced from the housing 50 a distance substantially equal to the
distance between the front end of the nose 86 and the cutter blade
108. Therefore, once the fixation instrument 22 has applied the
desired amount of tension in the strap 32, the free end 35 can be
cut in the manner described above to substantially remove the free
end 35 from the loop 55.
[0072] Referring now to FIGS. 4 and 6, the cutter assembly 72
further includes a safety mechanism 110 that moves from a
disengaged position, whereby the cutter arm 106 can move from the
seated disengaged position toward the engaged position, and an
engaged position that prevents the cutter arm 106 from moving from
the seated disengaged position toward the engaged position. In
accordance with the illustrated embodiment, the cutter assembly 72
includes a first engagement member 166 that extends down from the
cutter arm 106 and a second engagement member 168 that extends up
from the movable spring seat 132. When the tension assembly 70 is
in the first initial position, the first engagement member 166 is
spaced rearward from the movable spring seat 132. Otherwise stated,
the first engagement member 166 is spaced from the movable spring
seat 132 in the direction that the spring seat 132 moves when the
tension assembly 70 is moved from the first initial position toward
the third tension position. Accordingly, second engagement member
168 can move toward the first engagement member as the movable
spring seat 132 moves rearward. Alternatively, the second
engagement member 168 can extend from the traveler rod 111 and
movable along with the traveler rod 111 so as to interlock with the
engagement member 166.
[0073] The first and second engagement members 166 and 168 are
configured so as to interlock when they longitudinally overlap. For
instance, the second engagement member 168 can be configured as a
housing 170 having a slot 172 that receives the first engagement
member 166. The first engagement member 166 can define a flange 174
that overlaps the housing 170 in the transverse direction, such
that the flange 174 abuts the housing 170 when an engagement force
is applied to the cutter arm 106 along the direction of Arrow C so
as to move the cutter arm 106 from its seated disengaged position
toward its engaged position. In accordance with the illustrated
embodiment, the first and second engagement members 166 and 168
interfere so as to prevent the cutter arm 106 from being unseated
from the seat 158. It should be appreciated that the first
engagement members 166 and 168 can alternatively be sized and
shaped as desired so as to selectively interfere with each other in
the manner described herein.
[0074] Referring also to FIG. 8A, when the tension assembly 70 is
in the first initial position, the first and second engagement
members 166 and 168 are longitudinally spaced apart such that the
cutter arm 106 can be moved from the seated disengaged position to
the engaged position along the direction of Arrow C. When the
tension assembly 70 moves to the second grip position, the movable
spring seat 132 translates longitudinally rearward, thereby also
translating the second engagement member 168 longitudinally
rearward toward the first engagement member 166. In accordance with
the illustrated embodiment illustrated in FIG. 8B, the engagement
members 166 and 168 remain longitudinally spaced from each other
when the tension assembly 70 is in the second grip position,
thereby allowing the cutter arm 106 to become unseated and move
from the disengaged position toward the engaged position.
Accordingly, referring to FIG. 9, after the fixation instrument 22
has induced a desired amount of tension in the loop 55, the tension
assembly 70 can be moved to the grip position so as to capture the
free end 35 in the gap 116 prior to cutting the free end 35 in the
manner described above. Thus, as illustrated in FIG. 3A, the
plurality of bone fixation members 24 can be tightened about the
target bone 28 by actuating the tension assembly 70 as described
herein, and can be subsequently cut by actuating the cutter
assembly 72 as described herein.
[0075] In accordance with the illustrated embodiment shown in FIG.
8C, the engagement members 166 and 168 are positioned so as to
overlap when the tension assembly 70 has moved from the second grip
position toward the third tension position. Thus, once the tension
assembly 70 has advanced beyond the second grip position, the
engagement members 166 and 168 interfere when the engagement force
is applied to the cutter arm 106 along the direction of Arrow C.
Therefore, the safety mechanism 110 prevents the fixation
instrument 22 from cutting the free end 35 while the tension
assembly 70 is applying tension to the strap 32. Alternatively, the
engagement members 166 and 168 can be positioned so as to at least
partially overlap and interlock when the tension assembly 70 is in
the second grip position, thereby defining an interference that
prevents the cutter arm 106 from becoming unseated and moving to
the engagement position along the direction of Arrow C.
[0076] Referring now to FIGS. 11-15, the fixation instrument 22 can
include the safety mechanism 110, that in turn includes first
engagement member 166 and second engagement member 168 (the
interaction of which is described in detail above), and can further
include a second safety mechanism 195 that prevents the tension
assembly 70 from moving to the tightened position while cutter
assembly 72 is the actuated position. For instance, the second
safety mechanism can prevent the tension assembly from moving from
the partially engaged position to the tightened position as
illustrated, and can alternatively prevent the tension assembly 70
from moving from the disengaged position to the tightened position
while cutter assembly 72 is the actuated position. It can thus be
said that the second safety mechanism 195 can prevent the tension
assembly 70 from moving along a direction from the disengaged
position to the tightened position while cutter assembly 72 is the
actuated position. In this regard, it should be appreciated that
the safety mechanism 110 can be referred to as a first safety
mechanism. The second safety mechanism 195 can include at least one
safety member 196, such as first and second wings 161a and 161b
that extends from the rear end 159 of the spacer member 149, for
instance rearward along the longitudinal direction L toward the
rear end 78b of the body 76. In other embodiments, the wings 161a
and 161b do not extend from a spacer and are otherwise present
within fixation instrument 22 and provide the same functionality as
wings 161a and 161b that extend from the spacer member 149.
[0077] Each wing 161a and 161b can include a respective wing body
#a and #b, respectively, and a hook 163a, and 163b, respectively,
that extends out, for instance substantially perpendicularly down,
from the corresponding wing body #a and # substantially along the
transverse direction T. As illustrated in FIG. 12B, each wing 161a
and 161b defines a respective laterally outer face 165a and 165b
and an opposed laterally inner face 167a and 167b that is spaced
from the laterally outer face 165a and 165b along the lateral
direction A. Each hook 163a, 163b defines a longitudinally outer,
or front, end 169a and 169b, respectively, and an opposed rear end
171a and 171b that is spaced from the front end 169a and 169b along
the longitudinal direction L.
[0078] Referring to FIG. 12A, the fixation instrument 22 defines a
gap 173 that extends between the first and second wings 161a and
161b along the lateral direction A, such as between the inner faces
167a and 167b. The gap 173 is sized so as to receive the cutter arm
106 when the cutter arm 106 is in the disengaged position. For
instance, the inner faces 167a and 167b can define respective seats
that can support the cutter arm 106 when the cutter arm 106 is in
the disengaged position. For instance, the inner faces 167a and
167b can be contoured to abut a complementary outer surface of the
cutter arm 106 when the cutter arm 106 is in the disengaged
position at the upper transverse face of the body 76. Accordingly,
when the cutter arm 106 is seated in the gap 173, the cutter arm
106 can be said to be in a seated disengaged position.
[0079] As shown in FIGS. 14 and 15A-B, the cutter arm 106 may be
pivotally attached to the body 76, for instance at housing member
190b. In accordance with the illustrated embodiment, the cutter arm
106 is pivotally attached at its front end 107a to the nose 86 at a
pivot location 152 that defines a lateral pivot axis. This
arrangement is described above and depicted, for example, in FIGS.
7A-B. As shown in FIGS. 5A-B, 14, and 15A-B, cutter arm 106 can be
pivoted up and forward about the pivot location 152 along the
direction of Arrow C to its engaged position, which causes the
cutter blade 108 to travel down along an arc-shaped path toward the
complementary cutter blade 87 so as to reduce the size of gap 156.
This process is described above. In the embodiments depicted in
FIGS. 14 and 15A-B, pivoting of cutter arm 106 from its seated,
disengaged position to its engaged position involves removal of
cutter arm 106 from the gap 173. Accordingly, when cutter arm 106
is removed the gap 173, the cutter arm 106 can be said to be in an
engaged position.
[0080] At least one or both of the first and second wings 161a and
161b can be flexible, and can for instance be constructed from a
flexible material. Accordingly, at least one or both of the first
and second wings 161a and 161b can be movable between an
undeflected (or neutral) state and an outwardly deflected (for
instance laterally deflected) state. In the undeflected position,
shown in FIG. 15B, the first and second wings 161a and 161b are
substantially parallel to one another and the gap 173 defines a
first distance. The first and second wings 161a and 161b are in the
respective undeflected position when the cutter arm 106 is removed
from the gap 173, for instance once it is pivoted about the pivot
location 152 along the direction of Arrow C to its engaged
position. The first and second wings 161a and 161b are in the
respective deflected position when the cutter arm 106 is disposed
between the first and second wings 161a and 161b in the gap 173.
For instance, when the cutter arm 106 is in the seated, disengaged
position, it abuts the laterally inner face 167a of the first wing
161a and the laterally inner face 167b of the second wing 161b. As
illustrated in FIG. 12B, because the cross-sectional dimension of
cutter arm 106 along the lateral direction A is greater than the
gap 173 when the first and second wings 161a and 161b are in the
undeflected position, when the cutter arm 106 is moved to the
seated, disengaged position, the cutter arm 106 biases at least one
or both of the first and second wings 161a and 161b away from the
other of the first and second wings 161a and 161b to thereby
increase the lateral dimension of the gap 173 so that the cuter arm
106 can be seated in the gap 173 as described above. To facilitate
the deflection of wings 161a, 161b by cutter arm 106, laterally
inner face 167a of wing 161a and laterally inner face 167b of wing
161b may flare laterally inward toward each other as they extend
down along the transverse direction T so that the inner faces 167a
and 167b can define a non-zero angle with respect to the transverse
direction T.
[0081] When cutter arm 106 is in the seated, disengaged position,
and wings 161a, 161b are deflected laterally outwards, the distance
between laterally inner face 167a of wing 161a and laterally inner
face 167b of wing 161b along the lateral direction A, and thus the
lateral dimension of the gap 173, is greater than the corresponding
outer width of the second engagement member 168 along the lateral
direction A. FIG. 15B shows the lateral width w of second
engagement member, and FIG. 12B shows that the distance between
laterally inner face 167a of wing 161a and laterally inner face
167b of wing 161b is greater than the lateral width of second
engagement member 168, such that second engagement member 168,
along with movable spring seat 132, can travel in a direction along
longitudinal direction L towards rear end 78b of body 76 by passing
through the gap 173 between laterally inner face 167a of wing 161a
and laterally inner face 167b of wing 161b.
[0082] By contrast, as shown in FIG. 15B, when cutter arm 106 moves
from the seated, disengaged position to the engaged position, one
or both of the first and second wings 161a and 161b return to their
respective undeflected positions, and the distance between
laterally inner face 167a of wing 161a and laterally inner face
167b of wing 161b becomes less than the lateral width of second
engagement member 168. As described more fully below, in this
configuration, it is not possible for second engagement member 168
to pass between laterally inner face 167a of wing 161a and
laterally inner face 167b of wing 161b, and therefore not possible
for movable spring seat 132 (from which second engagement member
168 upwardly extends), to travel beyond a certain point towards
rear end 78b of body 76 in a direction along longitudinal direction
L. It should thus be appreciated that when one or both of the wings
161a and 161b is in the respective undeflected position, the
corresponding one or both of the wings 161a and 161b is at least
partially aligned with the second engagement member 168 along the
longitudinal direction L. Accordingly, the corresponding one or
both of the wings 161a and 161b is positioned to abut the second
engagement member 168 and prevent the second engagement member 168
from moving through the gap 173. When one or both of the wings 161a
and 161b is in the respective deflected position, the wings 161a
and 161b are offset with respect to the second engagement member
168 along the lateral direction A, such that the second engagement
member 168 is aligned with the gap 173 along the longitudinal
direction L, and thus is positioned to move at least into or
through the gap 173 past the first and second wings 161a and
161b.
[0083] As illustrated in FIG. 11, when the tension assembly 70
(described previously) is in the first initial position, both of
the hooks 163a and 163b and the first engagement member 166 are
spaced along the longitudinal direction L, for instance rearward,
from the movable spring seat 132 and second engagement member 168,
which extends upwardly from movable spring seat 132. When the user
applies the actuation force, for instance the rearwardly directed
force F, to grip portion 85 of trigger 84, the trigger 85 and thus
also the tension assembly 70 move from the first initial position
to the second grip position, which causes the movable spring seat
132 to translate rearward along traveler rod 111 in the
longitudinal direction towards the rear of end 78b of body 76. As
shown in FIGS. 14 and 15A-B, when the cutter arm 106 is in the
unseated, engaged position, the first and second wings 161a and
161b are in their respective undeflected positions. Accordingly,
when the tension assembly 70 moves from the first initial position
to the second grip position, the movable spring seat 132 moves
towards the rear end 78 until the second engagement member 168
abuts one or both of the first and second wings 161a and 161b, for
instance at the respective front longitudinal ends 169a and 169b of
the hooks 163a and 163b. Once second engagement member 168 abuts
the hooks 163a and 163b, for instance at the front longitudinal
ends 169a and 169b, interference between one or both of the wings
161a and 161b and the second engagement member 168 prevents the
tension assembly 70 from moving to the third tension position, for
instance from the second grip position, thereby preventing the
tension assembly 70 from increasing the tension in the strap 32
while cutter arm 106 is in the unseated, engaged position.
[0084] On the other hand, as illustrated in FIGS. 12A-B and 13,
when the cutter arm 106 is in the seated, disengaged position, the
wings 161a and 161b are in their respective deflected positions.
Accordingly, when the tension assembly 70 moves from the first
initial position to the second grip position, the movable spring
seat 132 is movable along the longitudinal direction L, for
instance rearwardly toward the rear end 78b, until second
engagement member 168 passes at least into or through the gap 173
between the wings 167a and 167b, for instance between the
respective laterally inner faces 167a and 167b. Because the wings
161a and 161b are offset from the second engagement member 168 when
the wings 161a and 161b are in the deflected position, the second
engagement member 168 does not abut the front longitudinal edges
169a and 169b of hooks 163a and 163b, respectively, so as to
prevent the second engagement member 168 from traveling into the
gap 173. As a result, when the wings 161a and 161b are in the
deflected position, the tensioning assembly 70 can be moved from
the second grip position to the third tightened position, thereby
increasing tension in the strap 32.
[0085] As described previously, the first and second engagement
members 166 and 168 are positioned so as to interlock when they
longitudinally overlap. Thus, in the embodiments depicted in FIGS.
11-15, the first and second engagement members 166 and 168 at least
partially overlap when the tension assembly is in the third tension
position, thereby defining interference that prevents the cutter
arm 106 from becoming unseated and moving to the engagement
position along the direction of Arrow C.
[0086] Although the disclosure has been described in detail, it
should be understood that various changes, substitutions, and
alterations can be made herein without departing from the spirit
and scope of the invention as defined by the appended claims.
Moreover, the scope of the present disclosure is not intended to be
limited to the particular embodiments described in the
specification. As one of ordinary skill in the art will readily
appreciate from the disclosure of the present invention, processes,
machines, manufacture, composition of matter, means, methods, or
steps, presently existing or later to be developed that perform
substantially the same function or achieve substantially the same
result as the corresponding embodiments described herein may be
utilized according to the present disclosure.
* * * * *